1. Field of the Invention
The present invention relates to volumetric calibration devices. In one of its aspects, the invention relates to a closed volumetric calibration system for liquid components in a polyurethane system.
2. State of the Prior Art
In the molding of polyurethane, isocynate, resin and other components are pumped to a mixing head. It is important that the components are in the proper ratios or the resulting polyurethane products will not be of the desired quality and specification. It is necessary to regularly check the dispensed amounts of various components to make certain that the ratios are constant. After checking the various amounts of dispensed components, the pumping device can be adjusted, if necessary, to correct the ratio.
In the past when it has been desired to conduct volumetric calibration or measuring operations on these circulating liquid materials, it has been the practice to take the components separately from the mixing head in a normal dispensing operation and to physically place each component in a cup to be weighed on a scale. This procedure takes substantial time in conducting a calibration. Further, exposure of the components to air created a high probability of contamination and the materials were customarily discarded. Further, the isocynate component can be noxious and there is the risk of danger to the person conducting the calibration. This procedure was thus somewhat time consuming and resulted in the waste of components.
To facilitate calibration of liquid materials, a special system with separate valves installed in the circulating system has been provided to meter liquid from the system. Such systems are cumbersome and still subject the worker to the chemical hazard. Further, the components cannot be returned to the circulating system without the risk of possible contamination.